The invention is concerned with a precision pressure gauge which enables continuous high precision measurement of the pressure of fluids, or gases and liquids.
Conventionally, a dead weight loading type standard pressure gauge is used for high precision measurement of the pressure of fluids.
FIG. 5 illustrates the principle of a dead weight loading type standard pressure gauge 51. The pressure gauge comprises a cylinder 52, a ram 53 fitted in the cylinder allowing its free ascent and descent, a cylinder chamber 54 formed below the ram inside the cylinder, a pressure pipe 55 installed on the cylinder which leads to the cylinder chamber, and a dead weight 56 to be loaded on the ram; this measures the pressure of fluids by equilibrating the pressure of fluids led into the cylinder chamber 54 through the aforementioned pressure pipe 55 with the weight of the dead weight 56.
An actual dead weight loading type standard pressure gauge is constructed so as to rotate a ram within a cylinder by means of a rotation driving mechanism in order that frictional resistances of the cylinder 52 against the ram 53 are reduced, thus resulting in the improvement of the measurement accuracy.
However, with a dead weight loading type standard pressure gauge such as this, a measurement of the pressure of fluids performed by equilibrating the weight of a dead weight with the pressure of fluids occasions the following difficulties:
(1) This method of measurement is both time and labor consuming because frequent changes and placements of the dead weight on the ram are necessary to ensure the weight of the dead weight and the pressure of fluids are in a state of equilibrium. In addition, the incorrect placement of a dead weight will damage the head of the ram.
(2) In the case of rapid and continuous change in the fluid being gauged, measurement can not be performed continuously.